[1] She has had roles in a number of movies and television series, most notably as Mona in Friends; she has also appeared in NYPD Blue, Grosse Pointe, The O.C., Cashmere Mafia, Without a Paddle, and Golden Boy.

She had a lead role as Lyne Danner in the CBS miniseries Shake, Rattle and Roll: An American Love Story (1999), in which she also sang.

[1] The series followed the set of a fictitious WB nighttime soap, also called Grosse Pointe, and several characters were based on real-life actors.

In 2003, Somerville landed a recurring role as Rachel Hoffman, a former colleague of Sandy Cohen, in the first season of Fox's teen drama series The O.C.. She appeared on the cover of Stuff magazine's May 2004 issue titled, "Girls of The O.C."

She portrayed Suzie Cavandish in the ABC Family romantic comedy film Labor Pains (2009) starring Lindsay Lohan.

In 2011, Somerville starred in the Hallmark Channel Christmas television film A Holiday Engagement, in which she sings the song "Angels We Have Heard On High".